baxsom

Ok,

I keep reading here that one of the best options for an intake upgrade on a LS5 454 is to put the aluminum intake off of a 68 or 69 390 horse 427.

Maybe I am just missing it but the question I have is why is that an upgrade. I mean I know it is aluminum over the cast iron so the weight is nice but other than the weight why is the L36 427 intake better than the LS5 454 intake.

thanks.

Durango_Boy

I may be mistaken, but I would think of the 427 as a higher RPm HP engine that needed a lot of air. The 454s were torque monsters that needed less air and for the most part were choked by the heads so a high flowing intake wouldn't have even helped much.

The 427 manifold probably does flow better than a 454 manifold.

CCrane65

So, to get any real benefit from the aluminum intake you should also port the heads.

cc

baxsom

I thought that they flowed more but does anyone know how much more.

I know that the 454 and L36 intake use oval parts so at least they match.

I was just wondering, the 427 intake on ebay is pretty cheap so it seems like a worthwhile investment.

0Road-Race Vette

You would get a great benefit by porting the heads no matter which intake you use. On an otherwise stock motor no matter which of those two intakes you use the performance will be about the same. The biggest benefit that particular aluminum intake will give you is a weight savings and a cooler running motor as the aluminum intake will dissapate heat a lot better,not a noticable performance gain. It is also an intake that will fit under your big block hood easily(if your car has one)

I would do it just for the first two reasons alone as long as you are not concerned about originality

carbster09

I bought an L 36 intake offof Ebay/Flea bay a few years ago. They don't come up very often and its one of the few that will fit under my LS5 intake without an worry. The look very similar so I don't care so much about the look. I will paint it orange after I get it ported and port matched to my ported heads. It seems like it should flow at least as good as a LS5 intake, is lighter weight and is Alum. Its a win-win solution. If you can pick it up for less than $250 I would buy it!

carbster09

Plus there is something cool about using factory parts and going fasterrrr!

vett us all

I USED A SQUARE PORT 427 OPEN PLENUM ALUMINUM INTAKE WITH OVAL PORT PORTED HEADS AND 990 CFM HOLLEY. 8700 RPM MOTOR WITH AN ERSON 99X SOLID CAM. 70 SS NOVA WOULD FLY. HAPPY JULY 4TH

DRIVESHAFT

Yep. Its easy to figure out why that setup shouldnt work, but I guess nobody ever told the engines.
For whatever reason, a rectangle port intake on oval port heads seems to defy logic and work pretty darn well.

baxsom

so the old LS6 intake should work pretty well also then?

DRIVESHAFT

I dont know anyone who has tried it with that particular intake, but it is likely that it would.

sxr6

427-390hp.....454-390 or 365hp
I may be mistaken but I think the intakes flow the exact same cfms.
Only diff is allum--steel or weight & little improved cooling.

brngrhd

the motor that came out of my vette has 435hp tri-power (rectangle port) and oval port head the top 3/8in blocked off. air flow goes along the top of the port..... so that meens that the air would be running along the top of the port and bam hit the edge of the port on the head great so now i'm betting it will run a lot better with the rectangle port pro-1 heads.

carbster09

I agree with SRX 6; they look pretty similiar to me; other then the 427/390 being Alum. I have compared the two side by side.

By the way do you have an SRX6? I always wanted one and would think about one for the right price!

In fact I saw one yesterday for the first time in ages. They sound neat with that big single piston thumping away

carbster

TheSkunkWorks

A rectangle port intake will work far better with oval port heads if you epoxy it up and match it.

sxr6

A SXR 6 is a three cylinder snowmachine

Knut-71

What sort of epoxy material did you use for this purpose? I have ordered a new LS-6 manifold and I am ready for some porting activities. How is this intake working for you? Did you replace it with something comparable? I am currently using an air-gap with L-88 hood, but would like to revert back to the original big-block hood. I have used a Torker-2 manifold in the past, but I am not sure the open plennum can provide the throttle response I am looking for. For the LS-6 intake, I will try to match it to a set of RPM-0 heads.

tnx

vette8121

just curious, who did you order a LS6 intake from...thanks

TheSkunkWorks

Knut-71, IMHO an LS-6 intake adapted to oval port heads is a great option. The one in my previous post belongs to yellow-fever, who had it done by a local shop here in Memphis at my advice. Feedback has been all . What's great about this mod is 1) LS-6 intake flows well for a low profile manifold, 2) it doesn't show, 3) you maintain a factory appearance, and 4) you can always hog it back out.

If you have the proper tools and have some experience matching manifolds you could probably do it yourself. Just make sure the runner cross sections end up with a relatively gradual tapper down to the intake ports as they approach the head. Moroso #35560 is the A&B epoxy.

http://www.moroso.com/catalog/catego...?catcode=22001

Knut-71

Reproduced LS6 intake manifolds are available on ebay. You can get them for $300. Casting quality appears to be good and I hope this will be my final intake purchase for this Corvette. When rebuilding the engine, I should probably have considered rectangular vs oval intake ports on my Edelbrock RPM heads. Anyway, from a first glance perspective, modification of the LS6 intake appears to be plausible.

Thanks

knut